Dibenzothiophene-containing materials in phosphorescent light emitting diodes

ABSTRACT

An organic light emitting device that includes an anode, a cathode, an enhancement layer, and an emissive layer that includes homoleptic iridium complexes containing phenyl-imidazole ligands, which include at least one fused substituent. The enhancement layer also includes a new dibenzothiophene and dibenzofuran-containing compound that is useful as a material in an enhancement layer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No.13/186,204, filed Jul. 19, 2011, which is a divisional of U.S.application Ser. No. 12/208,907, filed Sep. 11, 2008, which issued asU.S. Pat. No. 8,007,927 on Aug. 30, 2011, which claims priority to U.S.Provisional Application Ser. No. 61/017,480, filed Dec. 28, 2007, thedisclosures of which are herein expressly incorporated by reference intheir entirety. This application is also related to InternationalApplication No. PCT/IB2007/004687, filed Dec. 28, 2007.

PARTIES TO A JOINT RESEARCH AGREEMENT

The claimed invention was made by, on behalf of, and/or in connectionwith one or more of the following parties to a joint universitycorporation research agreement: Regents of the University of Michigan,Princeton University, The University of Southern California, and theUniversal Display Corporation. The agreement was in effect on and beforethe date the claimed invention was made, and the claimed invention wasmade as a result of activities undertaken within the scope of theagreement.

FIELD OF THE INVENTION

The present invention is directed to organic light emitting devices(OLEDs). More specifically, the present invention relates tophosphorescent light emitting materials and devices that may haveimproved device lifetime.

BACKGROUND

Opto-electronic devices that make use of organic materials are becomingincreasingly desirable for a number of reasons. Many of the materialsused to make such devices are relatively inexpensive, so organicopto-electronic devices have the potential for cost advantages overinorganic devices. In addition, the inherent properties of organicmaterials, such as their flexibility, may make them well suited forparticular applications such as fabrication on a flexible substrate.Examples of organic opto-electronic devices include organic lightemitting devices (OLEDs), organic phototransistors, organic photovoltaiccells, and organic photodetectors. For OLEDs, the organic materials mayhave performance advantages over conventional materials. For example,the wavelength at which an organic emissive layer emits light maygenerally be readily tuned with appropriate dopants.

OLEDs make use of thin organic films that emit light when voltage isapplied across the device. OLEDs are becoming an increasinglyinteresting technology for use in applications such as flat paneldisplays, illumination, and backlighting. Several OLED materials andconfigurations are described in U.S. Pat. Nos. 5,844,363, 6,303,238, and5,707,745, which are incorporated herein by reference in their entirety.

One application for phosphorescent emissive molecules is a full colordisplay. Industry standards for such a display call for pixels adaptedto emit particular colors, referred to as “saturated” colors. Inparticular, these standards call for saturated red, green, and bluepixels. Color may be measured using CIE coordinates, which are wellknown to the art.

One example of a green emissive molecule is tris(2-phenylpyridine)iridium, denoted Ir(ppy)₃, which has the structure of Formula I:

In this, and later figures herein, we depict the dative bond fromnitrogen to metal (here, Ir) as a straight line.

As used herein, the term “organic” includes polymeric materials as wellas small molecule organic materials that may be used to fabricateorganic opto-electronic devices. “Small molecule” refers to any organicmaterial that is not a polymer, and “small molecules” may actually bequite large. Small molecules may include repeat units in somecircumstances. For example, using a long chain alkyl group as asubstituent does not remove a molecule from the “small molecule” class.Small molecules may also be incorporated into polymers, for example as apendent group on a polymer backbone or as a part of the backbone. Smallmolecules may also serve as the core moiety of a dendrimer, whichconsists of a series of chemical shells built on the core moiety. Thecore moiety of a dendrimer may be a fluorescent or phosphorescent smallmolecule emitter. A dendrimer may be a “small molecule,” and it isbelieved that all dendrimers currently used in the field of OLEDs aresmall molecules.

As used herein, “top” means furthest away from the substrate, while“bottom” means closest to the substrate. Where a first layer isdescribed as “disposed over” a second layer, the first layer is disposedfurther away from substrate. There may be other layers between the firstand second layer, unless it is specified that the first layer is “incontact with” the second layer. For example, a cathode may be describedas “disposed over” an anode, even though there are various organiclayers in between.

As used herein, “solution processible” means capable of being dissolved,dispersed, or transported in and/or deposited from a liquid medium,either in solution or suspension form.

A ligand may be referred to as “photoactive” when it is believed thatthe ligand directly contributes to the photoactive properties of anemissive material. A ligand may be referred to as “ancillary” when it isbelieved that the ligand does not contribute to the photoactiveproperties of an emissive material, although an ancillary ligand mayalter the properties of a photoactive ligand.

As used herein, and as would be generally understood by one skilled inthe art, a first “Highest Occupied Molecular Orbital” (HOMO) or “LowestUnoccupied Molecular Orbital” (LUMO) energy level is “greater than” or“higher than” a second HOMO or LUMO energy level if the first energylevel is closer to the vacuum energy level. Since ionization potentials(IP) are measured as a negative energy relative to a vacuum level, ahigher HOMO energy level corresponds to an IP having a smaller absolutevalue (an IP that is less negative). Similarly, a higher LUMO energylevel corresponds to an electron affinity (EA) having a smaller absolutevalue (an EA that is less negative). On a conventional energy leveldiagram, with the vacuum level at the top, the LUMO energy level of amaterial is higher than the HOMO energy level of the same material. A“higher” HOMO or LUMO energy level appears closer to the top of such adiagram than a “lower” HOMO or LUMO energy level.

As used herein, and as would be generally understood by one skilled inthe art, a first work function is “greater than” or “higher than” asecond work function if the first work function has a higher absolutevalue. Because work functions are generally measured as negative numbersrelative to vacuum level, this means that a “higher” work function ismore negative. On a conventional energy level diagram, with the vacuumlevel at the top, a “higher” work function is illustrated as furtheraway from the vacuum level in the downward direction. Thus, thedefinitions of HOMO and LUMO energy levels follow a different conventionthan work functions.

More details on OLEDs, and the definitions described above, can be foundin U.S. Pat. No. 7,279,704, which is incorporated herein by reference inits entirety.

SUMMARY OF THE INVENTION

A new type of materials is provided. The new class of materials has adibenzothiophene-containing compound selected from the group consistingof:

where each of R₁ through R₆ are independently selected from the groupconsisting of any aryl and alkyl substituents and H, and where each ofR₁ through R₆ may represent multiple substitutions. In one aspect, allof R₁ through R₆ are H.

An organic light emitting device is also provided. The device has ananode, a cathode, an and an organic layer disposed between the anode andthe cathode. The organic layer further comprises a material containing acompound from the group consisting of Compound 1G through 12G, asdescribed above, with or without substituents. Preferably the organiclayer is an emissive layer having a host and an emissive dopant, and thecompound is the host. The compound may also preferably be used as amaterial in an enhancement layer.

New materials are provided. The materials have adibenzothiophene-containing and/or dibenzofuran-containing compoundselected from the group consisting of:

where each of R₁ through R₈ are independently selected from the groupconsisting of any aryl and alkyl substituents and H, and where each ofR₁ through R₈ may represent multiple substitutions. In one aspect, allof R₁ through R₈ are H.

An organic light emitting device is also provided. The device has ananode, a cathode, and an organic layer disposed between the anode andthe cathode. The organic layer further comprises a material containing acompound from the group consisting of Compound 2G through 35G, asdescribed above, with or without substituents. Preferably the organiclayer is an emissive layer having a host and an emissive dopant, and thecompound is the host. The compound may also preferably be used as amaterial in an enhancement layer.

A consumer product is also provided. The product contains a device thathas an anode, a cathode, and an organic layer disposed between the anodeand the cathode, where the organic layer further comprises a materialcontaining a compound from the group consisting of Compounds 2G through35G, as described above, with or without substituents.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an organic light emitting device.

FIG. 2 shows an inverted organic light emitting device that does nothave a separate electron transport layer.

FIG. 3 shows an organic light emitting device including compoundsdisclosed herein.

FIG. 4 shows a plot of normalized luminescence versus time for thedevice of FIG. 3.

FIG. 5 shows a plot of external quantum efficiency versus luminance forthe device of FIG. 3.

FIG. 6 shows a plot of power efficacy versus luminance for the device ofFIG. 3.

FIG. 7 shows a plot of luminance versus voltage for the device of FIG.3.

FIG. 8 shows a plot of EL intensity versus wavelength for the device ofFIG. 3.

FIG. 9 shows an organic light emitting device including compoundsdisclosed herein.

FIG. 10 shows a plot of external quantum efficiency versus luminance forthe device of FIG. 9.

FIG. 11 shows a plot of power efficacy versus luminance for the deviceof FIG. 9.

FIG. 12 shows a plot of luminance versus voltage for the device of FIG.9.

FIG. 13 shows a plot of EL intensity versus wavelength for the device ofFIG. 9.

FIG. 14 shows a dibenzothiophene-containing compound.

DETAILED DESCRIPTION

Generally, an OLED comprises at least one organic layer disposed betweenand electrically connected to an anode and a cathode. When a current isapplied, the anode injects holes and the cathode injects electrons intothe organic layer(s). The injected holes and electrons each migratetoward the oppositely charged electrode. When an electron and holelocalize on the same molecule, an “exciton,” which is a localizedelectron-hole pair having an excited energy state, is formed. Light isemitted when the exciton relaxes via a photoemissive mechanism. In somecases, the exciton may be localized on an excimer or an exciplex.Non-radiative mechanisms, such as thermal relaxation, may also occur,but are generally considered undesirable.

The initial OLEDs used emissive molecules that emitted light from theirsinglet states (“fluorescence”) as disclosed, for example, in U.S. Pat.No. 4,769,292, which is incorporated by reference in its entirety.Fluorescent emission generally occurs in a time frame of less than 10nanoseconds.

More recently, OLEDs having emissive materials that emit light fromtriplet states (“phosphorescence”) have been demonstrated. Baldo et al.,“Highly Efficient Phosphorescent Emission from OrganicElectroluminescent Devices,” Nature, vol. 395, 151-154, 1998;(“Baldo-I”) and Baldo et al., “Very high-efficiency green organiclight-emitting devices based on electrophosphorescence,” Appl. Phys.Lett., vol. 75, No. 3, 4-6 (1999) (“Baldo-II”), which are incorporatedby reference in their entireties. Phosphorescence is described in moredetail in U.S. Pat. No. 7,279,704 at cols. 5-6, which are incorporatedby reference.

FIG. 1 shows an organic light emitting device 100. The figures are notnecessarily drawn to scale. Device 100 may include a substrate 110, ananode 115, a hole injection layer 120 (HIL), a hole transport layer 125(HTL), an electron blocking layer 130, an emissive layer 135, a holeblocking layer 140, an electron transport layer 145, an electroninjection layer 150, a protective layer 155, and a cathode 160. Cathode160 is a compound cathode having a first conductive layer 162 and asecond conductive layer 164. Device 100 may be fabricated by depositingthe layers described, in order. The properties and functions of thesevarious layers, as well as example materials, are described in moredetail in U.S. Pat. No. 7,279,704 at cols. 6-10, which are incorporatedby reference.

More examples for each of these layers are available. For example, aflexible and transparent substrate-anode combination is disclosed inU.S. Pat. No. 5,844,363, which is incorporated by reference in itsentirety. An example of a p-doped hole transport layer is m-MTDATA dopedwith F.sub.4-TCNQ at a molar ratio of 50:1, as disclosed in U.S. PatentApplication Publication No. 2003/0230980, which is incorporated byreference in its entirety. Examples of emissive and host materials aredisclosed in U.S. Pat. No. 6,303,238 to Thompson et al., which isincorporated by reference in its entirety. An example of an n-dopedelectron transport layer is BPhen doped with Li at a molar ratio of 1:1,as disclosed in U.S. Patent Application Publication No. 2003/0230980,which is incorporated by reference in its entirety. U.S. Pat. Nos.5,703,436 and 5,707,745, which are incorporated by reference in theirentireties, disclose examples of cathodes including compound cathodeshaving a thin layer of metal such as Mg:Ag with an overlyingtransparent, electrically-conductive, sputter-deposited ITO layer. Thetheory and use of blocking layers is described in more detail in U.S.Pat. No. 6,097,147 and U.S. Patent Application Publication No.2003/0230980, which are incorporated by reference in their entireties.Examples of injection layers are provided in U.S. Patent ApplicationPublication No. 2004/0174116, which is incorporated by reference in itsentirety. A description of protective layers may be found in U.S. PatentApplication Publication No. 2004/0174116, which is incorporated byreference in its entirety. An “enhancement layer” occupies the sameposition in a device as a blocking layer described above, and may haveblocking functionality or other functionality that improves deviceperformance.

FIG. 2 shows an inverted OLED 200. The device includes a substrate 210,a cathode 215, an emissive layer 220, a hole transport layer 225, and ananode 230. Device 200 may be fabricated by depositing the layersdescribed, in order. Because the most common OLED configuration has acathode disposed over the anode, and device 200 has cathode 215 disposedunder anode 230, device 200 may be referred to as an “inverted” OLED.Materials similar to those described with respect to device 100 may beused in the corresponding layers of device 200. FIG. 2 provides oneexample of how some layers may be omitted from the structure of device100.

The simple layered structure illustrated in FIGS. 1 and 2 is provided byway of non-limiting example, and it is understood that embodiments ofthe invention may be used in connection with a wide variety of otherstructures. The specific materials and structures described areexemplary in nature, and other materials and structures may be used.Functional OLEDs may be achieved by combining the various layersdescribed in different ways, or layers may be omitted entirely, based ondesign, performance, and cost factors. Other layers not specificallydescribed may also be included. Materials other than those specificallydescribed may be used. Although many of the examples provided hereindescribe various layers as comprising a single material, it isunderstood that combinations of materials, such as a mixture of host anddopant, or more generally a mixture, may be used. Also, the layers mayhave various sublayers. The names given to the various layers herein arenot intended to be strictly limiting. For example, in device 200, holetransport layer 225 transports holes and injects holes into emissivelayer 220, and may be described as a hole transport layer or a holeinjection layer. In one embodiment, an OLED may be described as havingan “organic layer” disposed between a cathode and an anode. This organiclayer may comprise a single layer, or may further comprise multiplelayers of different organic materials as described, for example, withrespect to FIGS. 1 and 2.

Structures and materials not specifically described may also be used,such as OLEDs comprised of polymeric materials (PLEDs) such as disclosedin U.S. Pat. No. 5,247,190 to Friend et al., which is incorporated byreference in its entirety. By way of further example, OLEDs having asingle organic layer may be used. OLEDs may be stacked, for example asdescribed in U.S. Pat. No. 5,707,745 to Forrest et al, which isincorporated by reference in its entirety. The OLED structure maydeviate from the simple layered structure illustrated in FIGS. 1 and 2.For example, the substrate may include an angled reflective surface toimprove out-coupling, such as a mesa structure as described in U.S. Pat.No. 6,091,195 to Forrest et al., and/or a pit structure as described inU.S. Pat. No. 5,834,893 to Bulovic et al., which are incorporated byreference in their entireties.

Unless otherwise specified, any of the layers of the various embodimentsmay be deposited by any suitable method. For the organic layers,preferred methods include thermal evaporation, ink-jet, such asdescribed in U.S. Pat. Nos. 6,013,982 and 6,087,196, which areincorporated by reference in their entireties, organic vapor phasedeposition (OVPD), such as described in U.S. Pat. No. 6,337,102 toForrest et al., which is incorporated by reference in its entirety, anddeposition by organic vapor jet printing (OVJP), such as described inU.S. patent application Ser. No. 10/233,470, which is incorporated byreference in its entirety. Other suitable deposition methods includespin coating and other solution based processes. Solution basedprocesses are preferably carried out in nitrogen or an inert atmosphere.For the other layers, preferred methods include thermal evaporation.Preferred patterning methods include deposition through a mask, coldwelding such as described in U.S. Pat. Nos. 6,294,398 and 6,468,819,which are incorporated by reference in their entireties, and patterningassociated with some of the deposition methods such as ink-jet and OVJD.Other methods may also be used. The materials to be deposited may bemodified to make them compatible with a particular deposition method.For example, substituents such as alkyl and aryl groups, branched orunbranched, and preferably containing at least 3 carbons, may be used insmall molecules to enhance their ability to undergo solution processing.Substituents having 20 carbons or more may be used, and 3-20 carbons isa preferred range. Materials with asymmetric structures may have bettersolution processibility than those having symmetric structures, becauseasymmetric materials may have a lower tendency to recrystallize.Dendrimer substituents may be used to enhance the ability of smallmolecules to undergo solution processing.

Devices fabricated in accordance with embodiments of the invention maybe incorporated into a wide variety of consumer products, including flatpanel displays, computer monitors, televisions, billboards, lights forinterior or exterior illumination and/or signaling, heads up displays,fully transparent displays, flexible displays, laser printers,telephones, cell phones, personal digital assistants (PDAs), laptopcomputers, digital cameras, camcorders, viewfinders, micro-displays,vehicles, a large area wall, theater or stadium screen, or a sign.Various control mechanisms may be used to control devices fabricated inaccordance with the present invention, including passive matrix andactive matrix. Many of the devices are intended for use in a temperaturerange comfortable to humans, such as 18 degrees C. to 30 degrees C., andmore preferably at room temperature (20-25 degrees C.).

The materials and structures described herein may have applications indevices other than OLEDs. For example, other optoelectronic devices suchas organic solar cells and organic photodetectors may employ thematerials and structures. More generally, organic devices, such asorganic transistors, may employ the materials and structures.

The terms halo, halogen, alkyl, cycloalkyl, alkenyl, alkynyl, arylkyl,heterocyclic group, aryl, aromatic group, and heteroaryl are known tothe art, and are defined in U.S. Pat. No. 7,279,704 at cols. 31-32,which are incorporated herein by reference.

Dibenzo[b,d]thiophene (also referred to herein as“dibenzothiophene”)-containing materials are provided, which can be usedin the PHOLED devices fabricated by both vapor deposition or solutionprocessing, giving long lifetime stable devices with low voltage. Thematerials may be used as a stable host in PHOLED devices, or in otherlayers, such as an enhancement layer.

Compounds are provided comprising dibenzothiophene and/or dibenzofuran.Dibenzothiophenes and dibenzofurans may be used as hole and/or electrontransporting organic conductors, they usually exhibit more reversibleelectrochemical reduction in solution than some common organic groups,such as biphenyl. The triplet energies of dibenzothiophenes anddibenzofurans are relatively high. Therefore, a compound containingdibenzothiophene and/or dibenzofuran may be advantageously used as ahost or a material for an enhancement layer in PHOLED devices. Forexample, the triplet energy of dibenzothiophene is high enough for usein a blue or green PHOLED device. Dibenzothiophene and/ordibenzofuran-containing compounds may provide improved device stabilitywhile maintaining good device efficiency.

Dibenzothiophene-containing materials may have the following generalstructure:

Each of R₁ and R₂ may be independently selected from the groupconsisting of any alkyl, alkoxy, amino, alkenyl, alkynyl, arylkyl, aryl,heteroaryl, and hydrogen, and where R₁ and R₂ may represent multiplesubstitutions.

Particular dibenzothiophene compounds are provided, which may beadvantageously used in OLEDs, having the following structures:

Each of R₁ through R₆ are independently selected from the groupconsisting of any alkyl, alkoxy, amino, alkenyl, alkynyl, arylkyl, aryl,heteroaryl, and hydrogen, and where each of R₁ through R₆ may representmultiple substitutions.

Additionally, particular dibenzothiophene-containing compounds, whichmay be advantageously used in OLEDs, are provided:

Dibenzothiophene-containing and/or dibenzofuran-containing compounds areprovided, which may be advantageously used in OLEDs, having thefollowing structures:

Each of R₁ through R₈ are independently selected from the groupconsisting of any alkyl, alkoxy, amino, alkenyl, alkynyl, arylkyl, aryl,heteroaryl, and hydrogen, and where each of R₁ through R₈ may representmultiple substitutions.

Additionally, dibenzothiophene-containing and/or dibenzofuran-containingcompounds are provided, which may be advantageously used in OLEDs, areprovided:

As used herein, the following compounds have the following structures:

Particular host-dopant combinations for the emissive layer of an OLEDare also provided which may lead to devices having particularly goodproperties. Specifically, devices having an emissive layer using H1 asthe host and P1, P2, or P7 as an emissive dopant are demonstrated tohave particularly good properties. Such devices may be particularlyfavorable when the emissive layer includes two organic layers, a firstorganic layer including H1 doped with P1, and a second organic layerincluding H1 doped with P2, as illustrated in FIG. 3.

Similarly, devices having an emissive layer using Compound 1 as the hostand P3, P4 and/or P5 as dopants may lead to devices having particularlygood properties. Specifically, devices having an emissive layer usingCompound 1 as the host and P3 as an emissive dopant, and/or an emissivelayer with multiple dopants using Compound 1 as the host and P4 and P5as dopants, where P5 is the primary emissive dopant in the layer. Suchdevices may be particularly favorable when the emissive layer includestwo organic layers, a first organic layer including Compound 1 dopedwith P3, and a second organic layer including Compound 1 doped with P4and P5, as illustrated in FIG. 9.

Devices having an emissive layer using Compound 23 as the host and P1 asthe dopant may also lead to devices having particularly good properties.

Additionally, a consumer product comprising a device having an anode, acathode, and an organic layer, disposed between the anode and thecathode. The organic layer further comprises a material containing acompound selected from the group consisting of Compound 2G-35G where R₁through R₈ are independently selected from the group consisting of anyalkyl, alkoxy, amino, alkenyl, alkynyl, arylkyl, aryl, heteroaryl andhydrogen, and where each of R₁ through R₈ may represent multiplesubstitutions.

The materials described herein as useful for a particular layer in anorganic light emitting device may be used in combination with a widevariety of other materials present in the device. For example, emissivedopants disclosed herein may be used in conjunction with a wide varietyof hosts, transport layers, blocking layers, injection layers,electrodes and other layers that may be present. The materials describedor referred to below are non-limiting examples of materials that may beuseful in combination with the compounds disclosed herein, and one ofskill in the art can readily consult the literature to identify othermaterials that may be useful in combination.

In addition to and/or in combination with the materials disclosedherein, many hole injection materials, hole transporting materials, hostmaterials, dopant materials, exiton/hole blocking layer materials,electron transporting and electron injecting materials may be used in anOLED. Non-limiting examples of the materials that may be used in an OLEDin combination with materials disclosed herein are listed in Table 1below. Table 1 lists non-limiting classes of materials, non-limitingexamples of compounds for each class, and references that disclose thematerials.

TABLE 1 MATERIAL EXAMPLES OF MATERIAL PUBLICATIONS Hole injectionmaterials Phthalocyanine and porphryin compounds

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WO06098120, WO06103874 Exciton/hole blocking layer materialsBathocuprine compounds (e.g., BCP, BPhen)

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EXPERIMENTAL Compound Examples

Some of the dibenzothiophene-containing compounds were synthesized, asfollows:

Step 1. 3,3′-dihydroxybiphenyl (9.3 g, 50 mmol) was dissolved in 100 mLof CH₂Cl₂, followed by the addition of pyridine (15.8 g, 200 mmol). Tothis solution at −15° C., Tf₂O (42.3 g, 150 mmol) was added dropwise.The mixture was continued to stir at room temperature for 5 h. Theorganic phase was separated and washed with brine once. The crudeproduct was further purified by a silica column. 3,3′-ditriflatebiphenylwas obtained as pale white solid (21.3 g).

Step 2. To a 500 mL round flask was added 3,3′-ditriflatebiphenyl (2.7g, 6 mmol), 4-dibenzothiopheneboronic acid (4.1 g, 18 mmol), Pd₂(dba)₃(0.2 g, 0.2 mmol), 2-dicyclohexylphosphino-2′,6′-dimethoxybiphenyl (0.3g, 0.8 mmol), potassium phosphate tribasic (5.1 g, 24 mmol), and 150 mLof toluene. The reaction was heated to reflux and stirred under anitrogen atmosphere for 24 hours. After cooling, the mixture waspurified by a silica gel column. Yield was 2.6 g.

To a 500 mL round flask was added 2,2′-ditriflatebiphenyl (2.7 g, 6mmol), 4-dibenzothiopheneboronic acid (4.1 g, 18 mmol), Pd₂(dba)₃ (0.2g, 0.2 mmol), 2-dicyclohexylphosphino-2′,6′-dimethoxybiphenyl (0.3 g,0.8 mmol), potassium phosphate tribasic (5.1 g, 24 mmol), and 150 mL oftoluene. The reaction was heated to reflux and stirred under a nitrogenatmosphere for 24 hours. After cooling, the mixture was purified by asilica gel column. Yield was 2.5 g.

To a 500 mL round flask was added 4,6-diiododibenzothiophene (4.2 g, 9.6mmol), 4-dibenzothiopheneboronic acid (5.3 g, 23.1 mmol), Pd₂(dba)₃ (0.2g, 0.2 mmol), 2-dicyclohexylphosphino-2′,6′-dimethoxybiphenyl (0.3 g,0.8 mmol), potassium phosphate tribasic (7.4 g, 35 mmol), and 150 mL oftoluene. The reaction was heated to reflux and stirred under a nitrogenatmosphere for 24 hours. After cooling, the mixture was purified by asilica gel column. Yield was 2.4 g.

To a 500 mL round flask was added 4,6-diiododibenzothiophene (3.9 g, 8.9mmol), carbazole (3.3 g, 19.6 mmol), Pd₂(dba)₃ (0.2 g, 0.2 mmol),2-dicyclohexylphosphino-2′,6′-dimethoxybiphenyl (0.3 g, 0.8 mmol),sodium t-butoxide (5.8 g, 60 mmol), and 200 mL of xylene. The reactionwas heated to reflux and stirred under a nitrogen atmosphere for 24hours. After cooling, the mixture was purified by a silica gel column.Yield was 2.2 g.

Step 1. 2,6-Dibromo-1,3,5-trimethylbenzene (8.34 g, 30 mmol) wasdissolved in 50 ml of CHCl₃ and suspended with 1.0 g of iron powder in200 ml round-bottom flask. Bromine (2.00 ml, 31 mmol) was added dropwiseat room temperature and reaction mixture was heated to reflux for 3hours, cooled down to room temperature and stirred overnight. Solutionwas decanted, washed with NaOH 10% aq., filtered and evaporated. Thesolid residue was crystallized from chloroform, providing 7.00 g ofyellow solid (2,4,6-tribromo-1,3,5-trimethylbenzene).

Step 2. The 1 L round-bottom flask equipped with magnetic stirrer andreflux condenser was charged with 2,4,6-tribromo-1,3,5-trimethylbenzene(3.4 g, 9.5 mmol), 4-dibenzothiopheneboronic acid (8.7 g, 38 mmol),Pd₂(OAc)₂ (0.16 g, 0.7 mmol),2-dicyclohexylphosphino-2′,6′-dimethoxybiphenyl (0.46 g, 1.1 mmol),potassium phosphate tribasic (53 g, 250 mmol), 1.2 ml of water and 700mL of toluene. The reaction was heated to reflux and stirred under anitrogen atmosphere for 24 hours. After cooling, the mixture waspurified by a silica gel column. Yield was 5.2 g.

To a 500 mL round flask was added cyanuric chloride (1.5 g, 8.0 mmol),4-dibenzothiopheneboronic acid (6.8 g, 30 mmol), Pd₂(dba)₃ (0.2 g, 0.2mmol), 2-dicyclohexylphosphino-2′,6′-dimethoxybiphenyl (0.3 g, 0.8mmol), potassium phosphate tribasic (8.5 g, 40 mmol), and 250 mL oftoluene. The reaction was heated to reflux and stirred under a nitrogenatmosphere for 24 hours. After cooling, the mixture was filtered. Theproduct was further purified by recrystallization from EtOAc. Yield was3.0 g.

2,8-Dibromobenzothiophene (2.5 g, 7.3 mmol) in 150 mL of THF was treatedwith n-BuLi (1.6 M in hexane, 10 mL, 16 mmol) at −78° C. for 1 h.Dimesitylboron fluoride (5.0 g, 16.8 mmol) in 40 mL of ether was addeddropwise. After the mixture was stirred for another 1 h, the mixture wasslowly warmed up to room temperature and continued to stir overnight.The product was purified by a silica gel column. Yield was 2.8 g.

4-Dibenzothiopheneboronic acid (5.0 g) was suspended in 300 mL of xyleneand performed the Dean-Stark extraction for 5 h. After cooling down, thesolid was collected, washed with EtOAc and hexane, and sublimed at 320°C. twice. Yield was 3.6 g.

To a 500 mL round flask lithium amide (0.2 g, 10 mmol),4-iododibenzothiophene (9.9 g, 32 mmol), Pd₂(dba)₃ (0.2 g, 0.2 mmol),2-dicyclohexylphosphino-2′,4′,6′-triisopropylbiphenyl (0.4 g, 0.8 mmol),sodium t-butoxide (2.9 g, 30 mmol), and 200 mL of toluene were added.The reaction was heated to reflux and stirred under a nitrogenatmosphere for 24 hours. After cooling, the mixture was purified by asilica gel column. Yield was 4.0 g.

The 500 mL round flask was charged with 2,3-dibromobenzo[b]thiophene(5.0 g, 17.1 mmol), 4-dibenzothiopheneboronic acid (10.0 g, 43.8 mmol),Pd₂(PPh₃)₄ (0.8 g, 0.7 mmol), potassium carbonate (14.2 g, 103 mmol) in30 ml water followed by 200 ml of toluene. The reaction was heated toreflux and stirred under a nitrogen atmosphere for 24 hours. Aftercooling, separation of aqueous phase and evaporation the mixture waspurified by a silica gel column (hexane/ethyl acetate 4/1 mixture),providing target compound as solidified colorless oil (4.6 g).

Step 1. Dibenzothiophene (9.21 g, 50 mmol) was dissolved in 100 ml ofdry THF and solution was cooled to −50° C. n-BuLi (1.6 molar solution inhexanes, 40 ml, 64 mmol) was added dropwise. The reaction mixture waswarmed to room temperature, stirred for 4 hours and cooled to −30° C.Dibenzofluorenone (9.0 g, 50 mmol) in 70 ml THF was added dropwise,reaction mixture was allowed to warm to room temperature and stirredovernight. The reaction mixture was diluted with ethyl acetate (75 ml),washed with brine 3 times, dried over MgSO₄, filtered and evaporated.The solid residue was purified by column chromatography on silica(hexane/ethyl acetate 7/3) providing 12.0 g of9-(dibenzo[b,d]thiophen-4-yl)-9H-fluoren-9-ol as white solid.

Step 2. 9-(Dibenzo[b,d]thiophen-4-yl)-9H-fluoren-9-ol (product from theStep 1, 3.64 g, 10 mmol) were dissolved in 100 ml of dry toluene. Twentydrops of 10% solution of P₂O₅ in CH₃SO₃H were added at room temperature,and reaction mixture was stirred for 5 hours. The solution was decantedfrom solid residue, filtered through silica plug and evaporated. Thesolid residue was subjected to column chromatography (silica,hexane/ethyl acetate 4/1) providing 4.0 g of white solid.

Step 1. The 200 ml round-bottom flask equipped with reflux condenser andmagnetic stirrer was charged with carbazole (14.75 g, 88 mmol),3-iodobromobenzene (25.0 g, 88 mmol), Pd₂(dba)₃ (0.8 g, 0.85 mmol) anddppf (1,1′-bis(diphenylphosphino)ferrocene, 0.98 g, 1.8 mmol), sodiumt-buthoxide (25 g, 265 mmol) and 100 ml of dry xylene. Reaction mixturewas refluxed under N₂ atmosphere for 48 hours, cooled down to roomtemperature and evaporated. The solid residue was subjected to columnchromatography on silica (eluent—hexane/ethyl acetate 9/1) providing11.7 g of 9-(3-bromophenyl)-9H-carbazole as white solid.

Step 2. 9-(3-Bromophenyl)-9H-carbazole (11.7 g, 36 mmol),Bis(pinacolato)diboron (13.85 g, 54 mmol), potassium acetate (7.00 g, 71mmol), 1,1′-bis(diphenylphosphino)ferrocene]dichloropalladium (II) (0.6g) were dissolved in 100 ml of dry dioxane and refluxed under N₂atmosphere overnight. Then reaction mixture was cooled down to roomtemperature, diluted with ethyl acetate, washed with brine, dried overmagnesium sulfate, and evaporated. The solid residue was subjected tocolumn chromatography on silica (eluent hexane/ethyl acetate 5/1),providing 8.00 of9-(3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl)-9H-carbazoleas yellow solid. Analytically pure material may be prepared bycrystallization from hexane, otherwise product was used withoutadditional purification.

Step 3. 2-Bromoanisole (5.61 g, 30 mmol) and 4-dibenzothiopheneboronicacid (6.84 g, 30 mmol), Pd₂(PPh₃)₄ (1.00 g, 0.8 mmol) were dissolved in100 ml of toluene. Saturated solution of sodium carbonate (12.5 g inwater) was added, and reaction mixture was heated to reflux under N₂atmosphere overnight. Then reaction mixture was cooled down to roomtemperature, separated organic phase and evaporated toluene. The solidresidue was subjected to column chromatography on silica(eluent—hexane/ethyl acetate 4/1) providing4-(2-methoxyphenyl)dibenzo[b,d]thiophene as 6.6 g of colorlesssolidified oil.

Step 4. 4-(2-Methoxyphenyl)dibenzo[b,d]thiophene (6.6 g, 23 mmol) andpyridinium hydrochloride (27 g, 230 mmol) were mixed together, placed inthe 100 ml round bottom flask and heated to reflux for 45 min. Reactionmixture was cooled to 60° C., diluted with 100 ml water and extractedwith ethyl acetate. The organic phase was separated, dried overmagnesium sulfate, filtered and evaporated. The residue was subjected tocolumn chromatography on silica (eluent hexane/ethyl acetate 5/1),providing 4.00 g of 2-(dibenzo[b, d]thiophen-4-yl)phenol as clearsolidified oil.

Step 5. 2-(Dibenzo[b,d]thiophen-4-yl)phenol (3.9 g, 14 mmol) wasdissolved in 80 ml of dry dichloromethane, containing 5 ml of drypyridine, and solution was cooled in the ice bath. The triflic anhydride(5 ml, 28 mmol) was added dropwise, the reaction mixture was stirredovernight at room temperature, washed with water and evaporated. Theresidue was purified by column chromatography on silica (eluenthexane/ethyl acetate 9/1), providing 4.2 g of clear colorless solidifiedoil.

Step 6. The 200 ml round bottom flask with reflux condenser and magneticstirrer was charged with triflate from Step 5 (4.1 g, 10 mmol) andboronic ester from Step 2 (3.7 g, 10 mmol) followed by tribasicpotassium phosphate (6.36 g, 30 mmol), palladium acetate (0.67 g, 0.3mmol)), 2-dicyclohexylphosphino-2′,6′-dimethoxybiphenyl (0.8 g, 0.6mmol), 200 ml of toluene and 6 ml of water. The reaction was heated toreflux and stirred under a nitrogen atmosphere for 24 hours. Aftercooling, the mixture was purified by a silica gel column with eluenthexane/ethyl acetate 4/1, providing 2.8 g of target compound as whitesolid.

To a 500 mL round flask carbazole (3.7 g, 22 mmol),2,8-dibromobenzothiophene (3.4 g, 10 mmol), Pd(OAc)₂ (0.1 g, 0.5 mmol),tri-t-butylphosphine (1M in toluene, 1.5 mL, 1.5 mmol), sodiumt-butoxide (6.3 g, 66 mmol), and 200 mL of xylene were added. Thereaction was heated to reflux and stirred under a nitrogen atmospherefor 24 hours. After cooling, the mixture was purified by a silica gelcolumn. Yield was 4.7 g.

To a 500 mL round flask 4-iododibenzothiophene (6.2 g, 20 mmol),carbazole (4.0 g, 24 mmol), Pd₂(dba)₃ (0.9 g, 1.0 mmol),2-dicyclohexylphosphino-2′,6′-dimethoxybiphenyl (1.6 g, 4.0 mmol),sodium t-butoxide (5.8 g, 60 mmol), and 200 mL of xylene were added. Thereaction was heated to reflux and stirred under a nitrogen atmospherefor 24 hours. After cooling, the mixture was purified by a silica gelcolumn. Yield was 2.4 g.

m-Carborane (5.0 g, 35 mmol) in 200 mL of dry DME was treated withn-BuLi (1.6 M in hexane, 48 mL, 76 mmol) at 0° C. for 30 min undernitrogen. After the mixture was warm up to room temperature, CuCl (9.5g, 96 mmol) was added. The mixture continued to stir for 1 h, and 30 mLof dry pyridine, 4-iododibenzothiophene (22.6 g, 73 mmol) were added.The resulting mixture was refluxed for 60 h. After cooling, the mixturewas purified by a silica gel column. Yield was 1.8 g.

Step 1. Dibenzothiophene (27 g, 147 mmol) in 400 mL of THF was treatedslowly with n-BuLi (1.6 M in hexane, 100 mL, 160 mmol) at −50° C. Theresulting mixture was slowly warmed up to room temperature and continuedto stir for 5 h. The solution was cooled back to −78° C., DMF (61 mL) in100 mL of THF was added slowly. The mixture continued to stir foranother 2 h at this temperature and then warmed up to room temperature.The product was extracted with EtOAc and further purified by a silicagel column. Yield of 4-dibenzothiophenealdhyde was 21 g.

Step 2. To a 300 mL of THF solution of 2,8-dibromodibenzothiophene (3.4g, 10 mmol) at −78° C. was added slowly by n-BuLi (1.6 M in hexane, 13.8mL, 22 mmol). After stirred for 1 h at this temperature, the mixture wastreated slowly with a 100 mL of THF solution of4-dibenzothiophenealdhyde (4.2 g, 20 mmol). The solution was thenallowed to warm up to room temperature. The product was extracted withEtOAc and further purified by a silica gel column. Yield of dicarbinolintermediate was 4.2 g.

Step 3. To a 50 mL of CH₂Cl₂ solution of above dicarbinol intermediate(4.5 g, 7.4 mmol) and CF₃COOH (60 mL) was added portionwise of solidpowder of sodium borohydride (2.8 g, 74 mmol. The mixture was stirredunder nitrogen overnight. The solvents was removed by rotovap, and thesolid was washed with water then with NaHCO₃ solution. The crude productwas further purified by a silica gel column. Yield of final product was2.4 g.

Dibenzothiophene (14 g, 76 mmol) in 200 mL of THF was treated slowlywith n-BuLi (1.6 M in hexane, 50 mL, 80 mmol) at −50° C. The resultingmixture was slowly warmed up to room temperature and continued to stirfor 5 h. The solution was cooled back to −78° C., SiCl₄ (2.0 g, 12 mmol)was added slowly. The mixture continued to stir for another 2 h at thistemperature and 12 h at room temperature. The product was extracted withEtOAc and further purified by a silica gel column. Yield was 3.5 g.

To a 500 mL round flask 3,6-di(9-carbazolyl)carbazole (3.0 g, 6 mmol,prepared similarly as described above for 3-(9-carbazolyecarbazole),2-bromobenzothiophene (2.1 g, 7.8 mmol), CuI (0.4 g, 2.0 mmol),trans-1,2-Diaminocyclohexane (0.4 g, 3.6 mmol), potassium phosphatetribasic (3.2 g, 15 mmol), and 250 mL of toluene were added. Thereaction was heated to reflux and stirred under a nitrogen atmospherefor 24 hours. After cooling, the mixture was purified by a silica gelcolumn. Yield was 3.1 g.

The 300 mL round bottom flask, equipped with magnetic stirrer andrefluxed condenser, was charged with carbazole (7.1 g, 42.5 mmol),3-iodobromobenzene (25.00 g, 88 mmol), Pd₂(dba)₃ (800 mg, 1 mol %), dppf(1′,1′-bis(diphenylphosphino)ferrocene (975 mg, 2 mol %), sodiumt-buthoxide (6.3 g) and m-xylene (100 ml). The reaction mixture washeated to reflux and stirred under nitrogen atmosphere for 48 hours.Then reaction was cooled down to room temperature, filtered throughsilica plug and evaporated. The residue was subjected to columnchromatography on silica gel, eluent gradient mixturehexane-hexane/ethyl acetate mixture 9:1, providing 7.00 g of9-(3-bromo-phenyl)-9H-carbazole as white solid, structure was confirmedby NMR and GCMS spectroscopy.

7.00 g of 9-(3-bromo-phenyl)-9H-carbazole (21.7 mmol),bis-pinacolatodiborane (8.3 g, 32.7 mmol), potassium acetate (4.30 g)and (1,1′-bis(diphenylphosphino)-ferrocene)dichloropalladium (II) (500mg) were dissolved in 100 ml of dioxane and refluxed under nitrogen for24 hours. After evaporation the residue was subjected to columnchromatography on silica gel (eluent hexane/ethyl acetate 9/1 mixture),providing pure9-[3-(4,4,5,5-tetramethyl-[1,3,2]dioxaborolan-2-yl)-phenyl]-9H-carbazoleas white solid (11.8 g).

The 300 mL round bottom flask, equipped with magnetic stirrer andrefluxed condenser, was charged with 2,8-dibromo-dibenzothiophene (3.42g, 10 mmol),9-[3-(4,4,5,5-tetramethyl-[1,3,2]dioxaborolan-2-yl)-phenyl]-9H-carbazole(11.7 g, 30 mmol), palladium (II) acetate (64 mg),2-dicylohexylphosphino-2′,6′-dimethoxybiphenyl (234 mg), potassiumphosphate tribasic anhydrous (53.0 g), 700 ml of toluene and 2 nil ofwater. The reaction mixture was heated to reflux and stirred undernitrogen atmosphere for 24 hours. Then reaction was cooled down to roomtemperature, filtered through silica plug and evaporated. The residuewas washed with hexane, ethanol, water, ethanol and hexane, then wascrystallized from toluene. Sublimation (255° C. at 10⁻⁵ mm Hg) providedpure material (white solid, 2.0 g, structure confirmed by NMR.

2,6-Dimethoxyaniline (5.5 g, 0.036 mol), 2,2′-dibromobiphenyl (13.45 g,0.043 mol), sodium tert-butoxide (8.58 g, 0.089 mol) and Pd₂(dba)₃ (1.15g, 13 mmol) were charged into a 500 mL 3-neck flask with 300 mL ofanhydrous toluene. This flask was evacuated and back filled with N₂(this procedure was repeated a total of 3 times). Lastly, (9.6 mL, 96mmol) P(t-Bu)₃ 1.0 M in toluene was syringed into the reaction vesselthrough a septum. The reaction mixture was heated at reflux for 18 h.Heating was then discontinued. The reaction mixture was diluted with 200mL of water. The toluene layer was separated. The aqueous was extracted1×200 mL toluene. The toluene extracts were combined, were dried overmagnesium sulfate then were filtered and concentrated under vacuum.Silica gel chromatography of the crude product. Solvent system used was20-35% methylene chloride/hexanes.

9-(2,6-Dimethoxyphenyl)-9H-carbazole (10.00 g) and pyridiniumhydrochloride (50.0 g) were placed in the 250 ml round-bottom flask,equipped with magnetic stirrer and immersed in the pre-heated oil bath(230° C., 45 min) The reaction mixture was cooled down to roomtemperature, diluted with 400 ml water and extracted with ethyl acetate(3×150 ml). Organic fractions were combined, dried over sodium sulfateanhydrous, filtered and evaporated, providing 5.5 g of pure2-carbazol-9-yl-benzene-1,3-diol. 2-Carbazol-9-yl-benzene-1,3-diol (5.5g, 20 mmol) and pyridine (6.0 ml) were dissolved in 50 ml DCM(anhydrous) and cooled in the ice bath. Solution of triflic anhydride(6.0 ml) in 20 ml DCM was added dropwise upon intensive stirring,reaction mixture was warmed up to room temperature and stirredovernight. The reaction mixture was washed with water, dried over sodiumsulfate, filtered and evaporated, providing crude triflate. Purematerial (white solid, 6.0 g) was obtained by column chromatography onsilica gel (eluent hexane/ethyl acetate 1/1 mixture).

Bis-triflate (3.13 g, 5.8 mmol), 4-dibenzothiopheneboronic acid (3.30 g,14.5 mmol), Pd₂(dba)₃ (212 mg, 2 mol %),2-dicylohexylphosphino-2′,6′-dimethoxybiphenyl (190 mg, 4 mol %),potassium phosphate tribasic monohydrate (8.00 g), 100 ml of toluene and1 ml of water were refluxed in the round-bottom flask under nitrogenatmosphere for 24 hours, filtered hot through silica plug andevaporated. The residue was washed with hexane, ethanol, water, ethanoland hexane, then crystallized from toluene, providing pure material (4.1g).

2,6-Dimethoxyphenol (15.4 g, 0.1 mol) and 15 ml of pyridine weredissolved in 150 ml DCM and solution was cooled in the ice bath. Triflicanhydride was added dropwise upon vigorous stirring, reaction mixturewas allowed to warm up to room temperature, washed with water andevaporated. Kugelrohr distillation (200° C., 2 mm Hg) provided 25 g ofsolidified clear oil.

2,6-Dimethoxytriflate (8.58 g, 30 mmol), 4-dibenzothiopheneboronic acid(6.84 g, 30 mmol), potassium phosphate tribasic monohydrate (20.7 g),palladium (II) acetate (672 mg),2-dicylohexylphosphino-2′,6′-dimethoxybiphenyl (700 mg) and 150 ml oftoluene and 3 ml of water were heated to reflux and stifled undernitrogen atmosphere for 24 hours. Hot reaction mixture was filteredthrough silica plug and evaporated, the residue was subjected to columnchromatography on silica (eluent hexane/ethyl acetate 4/1 mixture),providing 4-(2,6-dimethoxyphenyl)-dibenzothiophene (9.00 g, prismcrystals from ethyl acetate).

4-(2,6-Dimethoxyphenyl)-dibenzothiophene (9.00 g) and pyridiniumhydrochloride (20 g) were placed in the 100 mL round-bottom flask,equipped with a magnetic stirrer. The flask was immersed in thepre-heated oil bath (220° C., 1 hour), cooled down to room temperatureand dissolved in 200 ml of water. The solution was extracted with ethylacetate (4×50 mL), organic fractions were combined, dried over sodiumsulfate, filtered and evaporated, providing2-(dibenzo[b,d]thiophen-4-yl)benzene-1,3-diol (7.2 g, white solid).

2-(Dibenzo[b,d]thiophen-4-yl)benzene-1,3-diol (7.2 g) was dissolved in150 mL of dry DCM, containing 15 mL of pyridine. Solution was cooled inthe ice bath, then triflic anhydride (18 mL in 25 mL of DCM) was addeddropwise. Reaction was allowed to warm up to room temperature and washedwith 10% sodium bicarbonate solution in water. DCM was evaporated, andthe residue was subjected to column chromatography, providing 14.5 g ofbis-triflate.

Triflate (5.56 g, 10 mmol), 4-dibenzothiopheneboronic acid (5.35 g, 25mmol), palladium (II) acetate (44 mg),2-dicylohexylphosphino-2′,6′-dimethoxybiphenyl (161 mg) and potassiumphosphate tribasic trihydrate (7.00 g) were suspended in 100 ml oftoluene and refluxed under nitrogen atmosphere for 24 hours. Hotreaction mixture was filtered and evaporated, the residue wascrystallized from toluene twice. Sublimation (245° C., mm Hg) provided5.0 g of target compound.

The 300 ml round-bottom flask equipped with reflux condenser andmagnetic stirrer was charged with 2,6-dimethoxytriflate (10.00 g, 35mmol), phenyl boronic acid (4.25 g, 35 mmol), potassium phosphatetribasic monohydrate (24.1 g), palladium (II) acetate (156 mg, 2 mol %),2-dicylohexylphosphino-2′,6′-dimethoxybiphenyl (573 mg, 4 mol %),toluene (100 ml) and water (2 ml). The reaction mixture was refluxedovernight, filtered through silica plug and evaporated. The residue wassubjected to column chromatography on silica gel (eluent hexane/ethylacetate 4/1 mixture), providing dimethoxybiphenyl as white solid (5.00g).

2,6-Dimethoxybiphenyl (5.00 g) and 15 g of pyridinium hydrochloride wereplaced in the round-bottom flask and immersed in the oil bath (210° C.,1.5 hours). Then the reaction was cooled down to room temperature,diluted with 200 ml of water and extracted with ethyl acetate (4×50 ml).Organic fractions were combined, dried over sodium sulfate andevaporated. The residue was subjected to column chromatography on silicagel (eluent hexane/ethyl acetate 1/1 mixture), providing 3.3 ofbiphenyl-2,6-diol as yellow solid.

Biphenyl-2,6-diol (7.2 g, 39 mmol) was dissolved in DCM (100 ml) andpyridine (10 ml). The solution was cooled in the ice bath, and triflicanhydride (27.3 g) was added dropwise upon vigorous stirring. Thereaction mixture was allowed to warm up to room temperature, was washedwith water, dried and evaporated. The residue was subjected to columnchromatography on silica gel (eluent hexane/ethyl acetate 4/1 mixture),providing 8.00 g of pure triflate.

The triflate (7.4 g, 16.4 mmol), 4-dibenzothiophene boronic acid (11.2g, 49 mmol), potassium phosphate tribasic monohydrate (22.7 g),palladium (II) acetate (70 mg),2-dicylohexylphosphino-2′,6′-dimethoxybiphenyl (270 mg) and 100 ml oftoluene were refluxed overnight under nitrogen atmosphere. The hotsolution was filtered through silica plug and evaporated. The residuewas crystallized hexane/ethyl acetate, providing target product as whitesolid (5.01 g). The material was additionally purified by sublimation(220° C., 10⁻⁵ mm Hg).

The 300 ml round-bottom flask equipped with reflux condenser andmagnetic stirrer was charged with 2-bromoaniline (8.00 g, 46.5 mmol),4-dibenzothiopheneboronic acid (10.5 g, 46.5 mmol), potassium carbonate(20 g, saturated solution in water),tetrakis(triphe-nylphoshine)palladium (0) (500 mg) and 100 ml oftoluene. The reaction mixture was refluxed overnight under nitrogenatmosphere, filtered through silica plug and evaporated. Product waspurified by column chromatography on silica gel, eluent hexane/ethylacetate 4/1 mixture, providing 2-(dibenzo[b,d]thiophen-4-yl)aniline(10.1 g) as yellow oil.

2-(Dibenzo[b,d]thiophen-4-yl)aniline (10.1 g, 36.4 mmol),2,2′-dibromobiphenyl (12.0 g, 38.5 mmol), sodium tert-butoxide (7.00 g,72.9 mmol), and Pd₂(dba)₃ (330 mg) were charged into a 500 mL 3-neckflask with 300 mL of anhydrous toluene. This flask was evacuated andback filled with N₂ (this procedure was repeated a total of 3 times).Lastly, (5 mL, 96 mmol) P(t-Bu)₃ 1.0 M in toluene was syringed into thereaction vessel through a septum. The reaction mixture was heated atreflux for 18 h. Heating was then discontinued. The reaction mixture wasdiluted with 200 mL of water. The toluene layer was separated. Theaqueous was extracted 1×200 mL toluene. The toluene extracts werecombined, were dried over magnesium sulfate then were filtered andconcentrated under vacuum. Crude material was washed with hexane andcrystallized from toluene-DCM. The material was additionally purified bysublimation (190° C., le mm Hg), providing 6.23 g of pure crystallinematerial.

The 300 mL round-bottom flask equipped with magnetic stirrer and refluxcondenser was charged with 2,6-dibromopyridine (2.20 g, 9.2 mmol),4-dibenzothiopheneboronic acid (4.62 g, 20 mmol), Pd₂(dba)₃ (180 mg),S-phos (220 mg), potassium triphosphate (6.00 g) and 100 mL of anhydroustoluene. The flask was filled with nitrogen, and solution was stirredunder reflux overnight. Then hot reaction mixture was filtered throughsilica plug, silica was washed with hot toluene. Organic fractions werecombined and evaporated. The residue was subjected to columnchromatography on silica gel (eluent hexane/ethyl acetate 4/1 mixture),providing target compound as white solid (3.01 g). Material wasadditionally purified by sublimation (225° C. at 10⁻⁵ mm Hg) and usedfor device fabrication.

Device Examples

All example devices were fabricated by high vacuum (<10⁻⁷ Torr) thermalevaporation. The anode electrode is ˜800 Å, 1200 Å or 2000 Å of indiumtin oxide (ITO), or 800 ÅSapphire/IZO. The cathode consists of 10 Å ofLiF followed by 1000 Å of Al. All devices are encapsulated with a glasslid sealed with an epoxy resin in a nitrogen glove box (<1 ppm of H₂Oand O₂) immediately after fabrication, and a moisture getter wasincorporated inside the package.

The organic stack of Device Examples 1-8 consisted of sequentially, fromthe ITO surface (1200 Å), 100 Å of P1 as the hole injection layer (HIL),300 Å of 4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (α-NPD) as thehole transporting layer (HTL), 300 Å of the invention compound dopedwith 10 or 15 wt % of an Ir phosphorescent compound as the emissivelayer (EML), 50 Å or 100 Å of HPT or the invention compound as the ETL2and 400 or 450 Å of tris-8-hydroxyquinoline aluminum (Alq₃) as the ETL1.

Comparative Example 1 was fabricated similarly to the Device Examplesexcept that CBP was used as the host.

The materials for the Emissive Layer, and the materials and thicknessesfor ETL 2 and ETL1, of Device Examples 1-8 are provided in Table 2. Thedevices were tested, and the results measured are provided in Table 3.Compound is abbreviated using the term Cmpd.

TABLE 2 ITO Device Dopant thick- Example Host wt % ETL2 (Å) ETL1 (Å)ness (Å) Compar- CBP P1 10% HPT (50) Alq₃ (450) 1200 ative 1 1 Cmpd 1 P110% Cmpd 1 (100) Alq₃ (400) 1200 2 Cmpd 1 P6 10% Cmpd 1 (100) Alq₃ (400)1200 3 Cmpd 1 P1 10% HPT (50) Alq₃ (450) 1200 4 Cmpd 1 P6 10% HPT (50)Alq₃ (450) 1200 5 Cmpd 2 P1 9% HPT (50) Alq₃ (400) 800 6 Cmpd 3 P1 9%HPT (50) Alq₃ (400) 800 7 Cmpd 4 P1 9% HPT (50) Alq₃ (400) 1200 8 Cmpd 5P1 9% HPT (50) Alq₃ (400) 1200

TABLE 3 At J = 40 Emission At L = 1000 cd/m² mA/cm² Device CIE max FWHMLE EQE PE L₀ LT_(80%) Example X Y (nm) (nm) V (V) (cd/A) (%) (lm/W)(cd/m²) (hr) Comparative 0.346 0.613 522 75 6.2 57.0 16 28.9 13,304 1051 1 0.337 0.619 523 73 7.4 48.2 13 20.5 13,611 325 2 0.328 0.620 520 737.4 36.8 10 15.6 12,284 340 3 0.338 0.618 524 73 6.3 60.3 17 30.1 13,683300 4 0.328 0.621 520 73 6.4 52 14.4 25.5 14,014 187 5 0.336 0.623 52472 5.9 53.8 15 28.7 16389 18 6 0.349 0.614 528 73 6.1 45.5 12 23.2 1567228 7 0.355 0.609 528 74 6.8 39.6 11 18.3 13403 98 8 0.353 0.613 528 726.3 49.5 14 24.7 15442 5.5

From Device Examples 1-8, it can be seen that the Invention Compounds ashosts in green phosphorescent OLEDs give high device efficiency (LE>35cd/A at 1000 cd/m²), indicating dibenzothiophene as a chromophore hastriplet energy high enough for efficient green electrophosphorescence.Most notably is the high stability of the device incorporating Compounds1 as the host. Device Example 3 and Comparative Example 1 are onlydifferent in the host. Device Example 3 uses Compound 1 as the hostwhereas Comparative Example 1 uses the commonly used host CBP. Thelifetime, T₈₀% (defined as the time required for the initial luminance,L₀, to decay to 80% of its value, at a constant current density of 40mA/cm² at room temperature) are 300 hours and 105 hours respectively,with Device Example 3 having a slightly higher L₀. This translates toalmost a 3 fold improvement in the device stability. The inventioncompounds may function well as the enhancement layer (ETL2). DeviceExample 1 and Device Example 3 both have Compound 1 as the host, butCompound 1 and 2,3,6,7,10,11-hexaphenyltriphenylene (HPT) as theenhancement layer respectively. They have T_(0.8) of 325 and 300 hoursrespectively with similar L₀ (˜13600 cd/m²), indicating the goodperformance of the invention compound as the enhancement layer.

The data suggest that arylbenzothiophenes, particularly biphenylsubstituted dibenzothiophenes, are excellent hosts and enhancement layerfor phosphorescent OLEDs, providing as least the same efficiency andmultiple times of improvement in stability compared to the commonly usedCBP as the host.

A number of devices were fabricated having two different doped emissivelayers, where the devices do not include a hole transport layer using amaterial such as NPD. Table 4 shows the structures for these devices.Table 5 shows measured experimental results for these devices. Ingeneral, the devices had an ITO anode, a hole injection layer of LG101™(purchased from LG Chemical, Korea), and an emissive layer having afirst organic layer and a second organic layer with an interface inbetween. Some of the devices had an enhancement layer (ETL2). All of thedevices had an electron transport layer (ETL1) of LG201, available fromthe same source as LG101. Devices 9-16 have first and second organiclayers with the same non-emissive materials, and differentphosphorescent materials, where the first organic layer additionallyincludes a lower energy emissive material. All of devices 9-16 includeemissive layers having a first and second organic layer with aninterface in between. In all of these devices, the concentration ofphosphorescent material is higher in the first (closer to anode) organiclayer. The materials and thicknesses for Device Examples 9-16 areprovided in Table 4. The devices were tested, and the results measuredare provided in Table 5. Compound is abbreviated using the term Cmpd.All percentages are wt % unless otherwise noted.

TABLE 4 Device Anode HIL EML1 EML2 ETL2 ETL1 9 ITO LG101 Cmpd 1: Cmpd 1:P3 (18%) none LG201 [1200 Å] [100 Å] P4 (30%):P5 (0.5%) [300 Å] [250 Å][300 Å] 10 ITO LG101 Cmpd 1: Cmpd 1: P3 (12%) none LG201 [1200 Å] [100Å] P4 (30%):P5 (0.5%) [300 Å] [250 Å] [300 Å] 11 ITO LG101 Cmpd 1: Cmpd1: P3 (24%) none LG201 [1200 Å] [100 Å] P4 (30%):P5 (0.5%) [300 Å] [250Å] [300 Å] 12 ITO LG101 Cmpd 1: Cmpd 1: P3 (24%) Cmpd 1 [50 Å] LG201[1200 Å] [100 Å] P4 (30%):P5 (0.5%) [300 Å] [250 Å] [300 Å] 13 ITO LG101Cmpd 1: Cmpd 1: P3 (18%) Cmpd 1 [50 Å] LG201 [1200 Å] [100 Å] P4(30%):P5 (0.5%) [300 Å] [250 Å] [300 Å] 14 ITO LG101 Cmpd 1: Cmpd 1: P3(12%) Cmpd 1 [50 Å] LG201 [1200 Å] [100 Å] P4 (30%):P5 (0.5%) [300 Å][250 Å] [300 Å] 15 ITO LG101 Cmpd 1: Cmpd 1: P3 (18%) Cmpd 1 [50 Å]LG201 [1200 Å] [200 Å] P4 (30%):P5 (0.5%) [200 Å] [250 Å] [300 Å] 16 ITOLG101 Cmpd 1: Cmpd 1: P3 (18%) Cmpd 1 [50 Å] LG201 [1200 Å] [100 Å] P4(30%):P5 (0.5%) [200 Å] [250 Å] [300 Å]

TABLE 5 At 1,000 cd/m² V LE EQE PE At 10 mA/cm² At L₀ = 1,000 cd/m²Device (V) (cd/A) (%) (lm/W) CIE x CIE y LT_(70%) (hr) LT_(60%) (hr) 96.1 23.7 10.9 12.3 0.467 0.457 Not measured Not measured 10 6.2 31.715.1 16.1 0.500 0.445 35,500 100,000 11 6.2 14.9 6.9 7.5 0.467 0.457 Notmeasured Not measured 12 6.1 29.5 13.5 15.2 0.456 0.460 78,000 140,00013 6.3 32.4 15.3 16.1 0.437 0.451 90,000 230,000 14 7.0 33.2 16.3 15.00.505 0.439 88,000 180,000 15 6.4 29.0 13.9 14.3 0.472 0.449 Notmeasured Not measured 16 6.2 29.4 14.2 14.9 0.467 0.448 Not measured Notmeasured

From Device Examples 9, 10 and 11, it can be seen that the efficiency ofthe device decreased with increasing concentration of P3, and the deviceCIE red-shifted with decreasing P3 concentration. Device Examples 9-11differ only in the concentration of the emissive compound P3 (i.e.,devices contain varying concentrations of P3) as all of Device Examples9-11 contained Inventive Compound 1 as the host, and were without ablocking layer between the EML and the LG201.

From Device Examples 12, 13, and 14, it can be seen that the efficiencyof the device decreased with increasing concentration of P3, the deviceCIE red-shifted with decreasing P3 concentration, and device operatingvoltage increased with decreasing concentration of P3. Devices 12-14differ only in the concentration of the emissive compounds P3, as all ofdevices 12-14 contained the inventive Compound 1 as the host and theblocking layer situated between the EML and ETL. Notably, Compound 1 isan efficient electron transport and blocking layer material, because theefficiency of each of Devices 12, 13, and 14 was shown to exceed that ofDevices 9, 10, and 11. Also, the electron stability of Compound 1 wasfound to be significant, because Devices 12-14 demonstrated an LT₆₀%stability that exceeded 100,000 hrs from 1,000 cd/m² initial luminance.

From Device Examples 15 and 16, it can be seen that the devices showvariation in device characteristics (e.g., CIE, efficiency) when theinjection layer LG101 thickness is varied (e.g., 200 Å versus 100 Å).

The organic stack of Device Examples 17-20 consisted of sequentially,from the ITO surface, 100 Å of P1 as the hole injection layer (HIL), 300Å of NPD as the hole transport layer (HTL), 300 Å of the inventioncompound doped with 10 wt % or 15 wt % of Pb, an Ir phosphorescentcompound, as the emissive layer (EML), 50 Å or 100 Å of HPT or theinvention compound as enhancement layer (ETL2), an electron transportlayer (ETL1) of Alq₃ having a thickness identified in Table 5, and aLiF/Al cathode. In particular, the BL and ETL have a sum total of 500 Å.Thus, the general device structure for the devices of Table 5 was:ITO(1200 Å)/P1 (100 Å)/NPD(300 Å)/Host: P1 x % (300 Å)/ETL2 (50 Å or 100Å)/Alq3 (400 Å or 450 Å)/LiF(10 Å)/Al(1000 Å).

TABLE 6 At 1000 cd/m² At 40 mA/cm² Device Host Dopant ETL2 ETL1 CIE VL.E. EQE PE L₀ LT_(80%) example Cmpd. x % (Å) (Å) X Y (V) (cd/A) (%)(lm/W) (cd/m²) (hr) 17 23 P1 10% 23 Alq₃ 0.355 0.605 7.1 42.2 11.7 18.6613,580 160 (100 Å) (400 Å) 18 23 P1 15% 23 Alq₃ 0.353 0.609 6.8 42.111.6 19.44 14,521 155 (100 Å) (450 Å) 19 23 P1 1% HPT Alq₃ 0.355 0.6076.8 46.9 13 21.66 14,728 94 (50 Å) (450 Å) 20 23 P1 15% HPT Alq₃ 0.3520.611 6.6 44.9 12.3 21.36 15,070 63 (50 Å) (400 Å)

The data in Table 6 describes the performance of Devices Examples 17-20.The voltage, luminous efficiency, external quantum efficiency and powerefficiency data were measured at 1000 cd/m² (display level brightness).The lifetime was measured at accelerated conditions: 40 ma/cm² DC. Theinitial device luminance (L₀) at life-test conditions (40 mA/cm²) isalso shown in Table 5. Compound 23 was used as a host for the greenphosphorescent emitter P1. Two different dopant concentrations (10% or15%) and two different ETL1 layers (Alq₃ of 400 Å or 450 Å) were variedin the devices and tested experimentally. The data show no significantdifference in the device performance due to dopant concentrationvariation. However, there was a difference in the device performance dueto variation in the ETL1 layer. In devices having HPT as the ETL1 layer,the device efficiency was slightly higher due to stronger BL propertiesof HPT. However, the lifetime of the devices with Compound 23 as theETL1 was longer. The data suggests that Compound 23 can be used as anefficient host for green phosphorescent emitter and as a ETL1 in thedevice. The stability of devices having Compound 23 as the ETL1 layer inthe devices is higher than the stability of devices having a similaroverall structure except with HPT as the ETL1 layer.

The organic stack of Device Examples 21-24 consisted of sequentially,from the anode surface, 100 Å of P1 or LG101 as the hole injection layer(HIL), 300 Å of NPD as the hole transport layer (HTL) or no HTL, 300 Åof the invention compound doped with 9 wt %, 15 wt % or 20 wt % of P2 orP7 Ir phosphorescent compounds as the emissive layer (EML), 50 Å, 150 Åor 250 Å of H1 as the enhancement layer (ETL2), and 200 Å, 300 Å or 400Å of Alq₃ as the electron transport layer (ETL1). The materials andthicknesses of Device Examples 21-24 are provided in Table 7. Thedevices were tested, and the corresponding results measured are providedin Table 8.

TABLE 7 De- vice Anode HIL HTL EML ETL2 ETL1 21 ITO LG101 none H1:P2 15%H1 Alq₃ [800 Å] [100 Å] [600 Å] [250 Å] [200 Å] 22 ITO LG101 NPD H1:P29% H1 Alq₃ [2000 Å] [100 Å] [300 Å] [300 Å] [50 Å] [400 Å] 23 ITO P1 NPDH1:P7 9% H1 Alq₃ [800 Å] [100 Å] [300 Å] [300 Å] [50 Å] [400 Å] 24Sapphire/ LG101 none H1:P7 20% H1 Alq₃ IZO[800 Å] [100 Å] [300 Å] [150Å] [300 Å]

TABLE 8 At 1000 cd/m² At L₀ = V LE EQE PE At 10 mA/cm² 1000 cd/m² Device(V) (cd/A) (%) (lm/W) CIE x CIE y LT_(80%) (hr) 21 12.9 10.0 5.3 2.40.160 0.285 352 22 7.6 10.9 6.6 4.5 0.155 0.234 77 23 9.0 12.1 6.0 4.20.162 0.317 151 24 7.1 8.9 5.5 4.0 0.145 0.232 205

From Devices 21, 22, 23, and 24 it can be seen that the devicesdemonstrate differences between device structures having an emissivelayer containing H1 and an emissive compound P2 or P7. Device Example 21did not have an HTL, and used a thick EML to enhance device operationalstability. The measured CIF, coordinates of Device Example 21 were notblue saturated, so the structures of Device Examples 22, 23, and 24 useda 30 nm EML. Device Example 22 also incorporated a 200 nm ITO layer tosaturate the device blue CIE. Device Example 23 was a standard bluePHOLED that was not optimized for operational stability. Device Example24 was a blue PHOLED using the same emissive compound P7 as used inDevice Example 23. However, Device Example 24 had several features thatenabled longevity such as no NPD, sapphire heat sink substrate, a thickblocking layer, and high emitter concentration. Hence, the LT₈₀% ofDevice Example 24 exceeded the LT₈₀% of Device Example 23, and DeviceExample 24 had improved blue CIE compared to Device Example 23.

FIG. 3 shows an organic light emitting device having only a layer with ahigh hole conductivity between an emissive layer and the anode, anenhancement layer of the same material used as a non-emissive host inthe emissive layer, and an emissive layer having first and secondorganic layers with different concentrations of phosphorescent materialand non-emissive materials, where the concentration of phosphorescentmaterial in the second organic layer is variable. The device of FIG. 3includes a 10 nm thick hole injection layer of LG101, a 30 nm thickfirst organic emissive layer of H1 doped with 30 wt % P2, a 30 nm thicksecond organic emissive layer of 1-11 doped with X wt % P2, a 25 nmthick enhancement layer of H1, a 20 nm thick electron transport layer ofAlq₃, and a LiF/Al cathode. X varies from 10 wt % to 18 wt % in thedevices fabricated, with devices at X=10, 14 and 18 wt % as indicated inthe legends for FIG. 4.

FIG. 4 shows a plot of normalized luminescence versus time for thedevice of FIG. 3.

FIG. 5 shows a plot of external quantum efficiency versus luminance forthe device of FIG. 3.

FIG. 6 shows a plot of power efficacy versus luminance for the device ofFIG. 3.

FIG. 7 shows a plot of luminance versus voltage for the device of FIG.3.

FIG. 8 shows a plot of EL intensity versus wavelength for the device ofFIG. 3.

FIG. 9 shows an organic light emitting device having only a layer with ahigh hole conductivity between an emissive layer and the anode, anenhancement layer of the same material used as a non-emissive host inthe emissive layer, and an emissive layer having first and secondorganic layers with different phosphorescent materials in the first andsecond organic layers, where the concentration of phosphorescentmaterial in the second organic emissive layer is variable. The device ofFIG. 9 includes a 10 nm thick hole injection layer of LG101, a 30 nmthick first organic emissive layer of H1 doped with 30 wt % P1, a 30 nmthick second organic emissive layer of H1 doped with X wt % P2, a 25 nmthick enhancement layer of H1, a 20 nm thick electron transport layer ofAlq₃, and a LiF/Al cathode. X varies from 10 wt % to 18 wt % in thedevices fabricated, with devices at X=10, 14 and 18 wt % as indicated inthe legends for FIG. 4. The device of FIG. 9 is very similar to that ofFIG. 3, with the difference being that the device of FIG. 9 usesdifferent emissive phosphorescent material in the first and secondorganic emissive layers, while the device of FIG. 3 uses the samephosphorescent material in both layers. The concentrations of thephosphorescent materials are the same in the device of FIG. 3 comparedto the device of FIG. 9.

FIG. 10 shows a plot of external quantum efficiency versus luminance forthe device of FIG. 9.

FIG. 11 shows a plot of power efficacy versus luminance for the deviceof FIG. 9.

FIG. 12 shows a plot of luminance versus voltage for the device of FIG.9.

FIG. 13 shows a plot of EL intensity versus wavelength for the device ofFIG. 9.

The device of FIG. 9 may be compared to the device of FIG. 3. In termsof device architecture, the devices are similar except in the emissivelayer, where the device of FIG. 9 has an emissive layer doped withphosphorescent emitter P1 and another emissive layer dopedphosphorescent emitter P2, whereas the device of FIG. 3 has onlyphosphorescent emitter P2. Both devices have a step in dopantconcentration, and similar concentrations even in the layers where theactual dopant is different. Several points can be understood fromcomparing these two device architectures. First, the device of FIG. 9exhibits a broad emission spectra that is a combination of emission fromboth P1 and P2. As a result, it can be inferred that the device of FIG.3 is emitting from both the layer doped with 30% P2 and the layer dopedwith a lesser concentration of P2. Comparing FIG. 5 to FIG. 10, it canbe seen that the device of FIG. 9 has better charge balance than thedevice of FIG. 3, as evidenced by a relatively flat external quantumefficiency over three orders of magnitude for the device of FIG. 9 ascompared to two orders of magnitude for the device of FIG. 3.

It is understood that the various embodiments described herein are byway of example only, and are not intended to limit the scope of theinvention. For example, many of the materials and structures describedherein may be substituted with other materials and structures withoutdeviating from the spirit of the invention. The present invention asclaimed may therefore includes variations from the particular examplesand preferred embodiments described herein, as will be apparent to oneof skill in the art. It is understood that various theories as to whythe invention works are not intended to be limiting.

1. An organic light emitting device, comprising: an anode; a cathode; an emissive layer; and an enhancement layer, wherein

is in the enhancement layer; wherein the emissive layer comprises an emissive dopant selected from the group consisting of:

wherein R₁, R₂, and R₃ are independently selected from the group consisting of any alkyl, alkoxy, amino, alkenyl, alkynyl, arylkyl, aryl, heteroaryl, and hydrogen, wherein (a) R₁ and R₃ form a fused ring that is, optionally, further substituted, (b) R₂ and R₃ form a fused ring that is, optionally, further substituted, or (c) both.
 2. The device of claim 1, wherein R₂ and R₃ form a fused ring that is, optionally, further substituted.
 3. The device of claim 2, wherein the emissive dopant comprises:


4. The device of claim 2, wherein the emissive dopant comprises:


5. The device of claim 1, wherein the emissive layer comprises H1 as a host.
 6. The device of claim 1, wherein the enhancement layer is a hole blocking layer. 